The Swedish patent application No. 7612217-5 describes a method to produce an iron powder containing copper, which has a low risk of segregation and dusting at the same time as the powder properties are maintained. According to this method the powder is produced by an annealing treatment of a mixture of iron and copper powder, at which a so-called partially diffusion alloy between iron and copper is obtained.
As certain alloying elements, such as e.g. phosphorus in the form of a ferrophosphorus powder and carbon in the form of graphite powder, cannot be sufficiently diffusion alloyed with an iron or steel powder without deteriorating the compressibility, there is a risk that mixtures in which these alloying elements are used are prone to segregation and/or dusting.
The Swedish patent application No. 8001764-3 describes a method to prevent segregation and/or dusting by adding to a powder mixture up to 1% of a sticky binder, which does not change its sticky properties with time at normal temperatures. However, it has been found that when binding agents of this nature are added to a dry powder mix the amount, which can be added, is controlled by the characteristic flowability of the powder mix. The amount which can be used with regard to the flow results in a decreased bonding effect between the iron particles and the particles of the alloying elements, why an optimal powder mix from segregation/dusting point of view cannot be obtained.